This invention relates to a cleaning solution that is useful for removing adhesives from the surfaces of hard substrates.
Adhesives are often applied industrially by a process involving transferring a wet adhesive to a machine part, then transfering the adhesive from the machine part to the material being adhered. For example, in the process of applying labels to beverage containers, high speed machines are used which transfer adhesive films, while wet, to pallets. The adhesive is then transfered from the pallet to a label picked from a label stack. Once coated with adhesive, the label is contacted with a container for permanent adhesion.
Machine parts which come in contact with adhesives need regular cleaning and maintenance on both a daily and longer-term basis to remove residual and built-up adhesive. The adhesives can be difficult to remove from machine parts, and the cleaning process is sometimes time-consuming. Conventional cleaning methods are not adequate for removing many adhesives, such as resin adhesives frequently used in the bottle labeling market. Solvents and harsh abrasives clean well, but can deteriorate machine parts, such as rubber pallets.
U.S. Pat. No. 4,370,174 describes the removal of adhesives from floors with a cleaning solution containing 40-80 weight percent of an organic solvent, an inorganic solid absorbent powder, and two surfactants. Such a solution contains both organic solvents and abrasives, which tend to deteriorate rubber parts often found on machinery.
U.S. Pat. No. 6,017,863 describes an aqueous cleaning solution for removing uncured adhesive resins from substrates. The cleaning solution contains a surfactant mixture of N-alkyl-2-pyrrolidone and an aminocarboxylic acid surfactant. It has been found, however, that aqueous surfactant solutions containing only surfactants and water are ineffective for removing many adhesives, and especially resin-based adhesives.
The problem solved by the present invention was to find a cleaning solution which effectively removes the adhesive from machine parts without damaging said parts. Surprisingly it has been found that an aqueous solution of a chaotropic agent and some surfactant is effective in removing many types of aqueous-based adhesives from the surfaces of hard substrates. Some advantages seen with the cleaning composition of the present invention are that it provides a effective cleaning solution for cleaning surfaces of hard-to-remove adhesives, it doesn""t harm hard surfaces, and it is safer than volatile compositions currently in use.
Accordingly it is an object of the present invention to provide an aqueous cleaning solution effective in removing adhesives from a hard substrate, and especially resin-based adhesives, from hard substrates. Specifically the invention provides a cleaning composition for removing adhesive from a hard substrate comprising:
a) 25 to 98 percent by weight of water;
b) 5 to 74 percent by weight of a chaotropic agent; and
c) 0.001 to 10 percent by weight of a surfactant.
Another object of the present invention is directed to a method for removing an adhesive from a hard substrate comprising forming a cleaning composition comprising:
a) forming a cleaning composition comprising:
1) 25 to 98 percent by weight of water;
2) 5 to 74 percent by weight of a chaotropic agent; and
3) 0.001 to 10 percent by weight of a surfactant; and
b) contacting said cleaning composition with an adhesive on a hard substrate.
The cleaning composition of the present invention is an aqueous solution containing a chaotropic agent and a surfactant.
A chaotropic agent is a chemical having hydrogen bonding capability, and that capability can be used to break apart molecules. Chaotropic agents loosen intermolecular and intramolecular interactions, such as hydrogen bonds and dipoles, forcing molecules to break apart. While not being bound to any theory, it is believed that chaotropic agents of the present invention act to break apart adhesive molecules by reducing and breaking hydrogen bonding and other interactions, making the adhesives easier to clean from surfaces.
The cleaning composition of the present invention contains from 5 to 74 percent by weight of a chaotropic agent, preferably 10 to 50 percent by weight. Preferred chaotropic agents for use in the cleaning solution include urea and guanadine hydrochloride, most preferably urea.
The cleaning composition of the present invention also includes at least one surfactant. Any surfactant is useful in the invention, including anionic, cationic, non-ionic, or amphoteric surfactants, or mixtures thereof. Preferred surfactants include anionic and non-ionic surfactants, most preferably anionic surfactants. The surfactant is present at from 0.001 to 10 weight percent of the solution, depending on the surfactant. A preferred surfactant concentration is from 0.5 to 2 percent by weight.
In addition to the chaotropic agent and surfactant, the aqueous cleaning solution of this invention may contain one or more additives conventionally used in aqueous cleaning solutions. Such additives include, but are not limited to, polysaccharides, d-limonene, solvents, perfumes, masking agents, defoamers, and preservatives.
Polysaccharide additives are useful in the cleaning solution. A preferred polysaccharide is starch. Polysaccharides are preferably present in the cleaning composition at up to 5 percent by weight, and most preferably at up to 2 percent by weight of the cleaning solution.
Solvents and masking agents known in the art may also be used in the cleaning composition. These additives include ethanol and polypropylene glycol.
Defoamers for use herein include stearates, silicone oils and adducts of ethylene oxide or propylene oxide with a C12-18 fatty alcohol. Defoamers in the present invention are preferably used at up to 1 percent by weight of the cleaning solution.
Preservatives for use herein include those conventionally used in aqueous adhesives such as benzoates, amides and fluorides. Also included are the hydroxybenzoic acid esters such as p-hydroxybenzoic acid methyl ester or p-hydroxybenzoic butyl ester. The preservatives may be present at up to 0.5 percent by weight in the cleaning composition.
The cleaning composition may be formed by several methods known in the art, including, but not limited to, combining the components with stirring, and forming an aqueous concentrate which is then diluted with water to form an aqueous solution.
An example of a process for forming the cleaning composition of the present invention would be to combine 49.35 percent by weight of water with 49.35 percent by weight of urea, based on the total cleaning composition, heating the combination to 110xc2x0 F., and then stirring for 20 minutes. To the aqueous urea solution are then added 1.0 percent of a sodium sulfosuccinate solution, 0.2 percent of a defoamer, and 0.1 percent of a preservative, by weight based on the total cleaning composition, and the mixture is then stirred for 30 minutes to form the cleaning composition.
The present invention is also directed to a process for removing adhesives from the surfaces of hard substrates.
Adhesives removable by the cleaning composition of the present invention are aqueous-based solution and emulsion adhesives. The adhesives are removable with the cleaning composition when they are in both the wet and dry state. These include, but are not limited to: synthetic adhesives based on ethylene vinyl acetate, polyvinyl alcohol, polyvinyl acetate, acrylics and polyurethane; resin products; animal glues; and natural polymers, such as those based on casein and starch. Aqueous-based adhesives may be formulated with additives such as tackifiers, thickeners, plasticizers, defoamers, preservatives, rheology modifiers, humectants, fillers, crosslinkers utilized in conventional amounts. The cleaning solution of the invention is useful in removing adhesives used in many areas of manufacturing including, for example, bottle labeling, tissue towel, cigarettes, bag lamination, envelopes, non-contact extrusion, folding cartons, window patch, lumber and wood, folding carton wheel and pressure sensitive label adhesive applications.
The cleaning solution of the present invention is useful for cleaning adhesives from the surfaces of hard substrates. Hard substrates include machine parts, floors, counters, tanks, tank trucks, tableware, piping and other hard materials which may be intentionally or accidentally contacted with an adhesive. Machine parts include those parts made of stainless steel, aluminum and other metals and alloys, ceramics, stone, and rubber, such as neoprene and nitrile rubber. The cleaning solution is also useful in the removal of adhesives from other hard substrates such as glass and plastics.
The cleaning solution of the invention is used to remove adhesive from surfaces of hard substrates by contacting the solution with the adhesive on said surfaces. The cleaning solution may be applied to the hard substrate by any method known in the art. Examples of such methods include, but are not limited to, immersion techniques, spray techniques including both hosing or pumping from a pump bottle, and mechanical brushing. The addition of energy increases the effectiveness of the cleaning solution in removing adhesives. Such energy may be added in the form of mechanical energy, such as stirring or scrubbing; heating the solution to temperatures below the boiling point of the cleaning composition; sonic energy, or any other energy form known in the art.
In practice, the cleaning composition may also be used in a diluted form. One method for using the cleaning composition is to add the composition to a tank which contains water. This may be followed by heating and/or stirring, such as in a boil out. The water can then be drained from the tank.